When somebody starts telling me that their OS magically makes applications run without using any CPU I know it's time to look somewhere else for information.
That's not what I said. What I said was that OS X does a better job of multitasking than does Windows... in other words, it does a better job of sharing the resources and dividing the attention of the CPU and memory without slowing the system. No magic about it. It will be getting even better with Snow Leopard's Grand Central Dispatch, which is designed to better take advantage of multiple core CPUs.
When I can have a dozen to 20 applications running simultaneously without apparent impact on response time on an OS X system but a Windows system starts to bog down with only three similar apps running, then the OS X system is observably better at multitasking... which makes it and me more productive.